Russian President Vladimir Putin on Sunday slammed the United States and Israel's killing of Iran's supreme leader Ayatollah Ali Khamenei as a "cynical violation" of morality and law.

Tehran has stood by as one of Russia's closest allies throughout Moscow's Ukraine offensive, and the Kremlin had earlier called for restraint in the run-up to the US-Israeli strikes on Iran. 

On Sunday, the Kremlin published a message that Putin sent to Iranian counterpart Masoud Pezeshkian in which the Russian leader expressed his "deepest condolences for the assassination of" Khamenei.

He said the killing was "carried out in a cynical violation of all norms of human morality and international law".

Putin said Khamenei "will be remembered as an outstanding statesman who made an enormous personal contribution to the development of friendly Russian-Iranian relations".

He asked Pezeshkian to "convey my most sincere sympathy and support to the relatives and loved ones of the Supreme Leader, to the government and to the entire people of Iran".

Russian foreign ministry on Sunday said Khamenei's death as well as other top Iranian officials was "met with outrage and deep regret in Moscow".

Russia "resolutely and consistently condemns the practice of political assassinations and the 'hunting' of leaders of sovereign states", the ministry added.

It called for "an immediate de-escalation, a cessation of hostilities, and a return to the political and diplomatic process".

On Saturday Moscow condemned the strikes on Iran warning they could spark "catastrophe" in the region.

Also Saturday, Russia's top diplomat Sergei Lavrov spoke by phone with Iranian counterpart Abbas Araghchi, with the Russian ministry stressing that the call was held "at the initiative of the Iranian side".

In 2025, Russia and Iran signed a strategic partnership treaty aimed at strengthening ties -- including in military matters.